Re: [PATCH bpf-next 7/7] tools/bpftool: add perf subcommand

Jakub Kicinski
2018-05-16T04:41:49Z

On Tue, 15 May 2018 16:45:21 -0700, Yonghong Song wrote:
> The new command "bpftool perf [show]" will traverse
> all processes under /proc, and if any fd is associated
> with a perf event, it will print out related perf event
> information.
>
> Below is an example to show the results using bcc commands.
> Running the following 4 bcc commands:
> kprobe: trace.py '__x64_sys_nanosleep'
> kretprobe: trace.py 'r::__x64_sys_nanosleep'
> tracepoint: trace.py 't:syscalls:sys_enter_nanosleep'
> uprobe: trace.py 'p:/home/yhs/a.out:main'
>
> The bpftool command line and result:
>
> $ bpftool perf
> 21711: prog_id 5 kprobe func __x64_sys_write offset 0
> 21765: prog_id 7 kretprobe func __x64_sys_nanosleep offset 0
> 21767: prog_id 8 tracepoint sys_enter_nanosleep
> 21800: prog_id 9 uprobe filename /home/yhs/a.out offset 1159
>
> $ bpftool -j perf
> {"pid":21711,"prog_id":5,"prog_info":"kprobe","func":"__x64_sys_write","offset":0}, \
> {"pid":21765,"prog_id":7,"prog_info":"kretprobe","func":"__x64_sys_nanosleep","offset":0}, \
> {"pid":21767,"prog_id":8,"prog_info":"tracepoint","tracepoint":"sys_enter_nanosleep"}, \
> {"pid":21800,"prog_id":9,"prog_info":"uprobe","filename":"/home/yhs/a.out","offset":1159}

You need to wrap the objects inside an array, so

if (json_output)
jsonw_start_array(json_wtr);
nftw();
if (json_output)
jsonw_end_array(json_wtr);

otherwise output will not be a valid JSON. To validate JSON try:

$ bpftool -j perf | python -m json.tool

> $ bpftool prog
> 5: kprobe name probe___x64_sys tag e495a0c82f2c7a8d gpl
> loaded_at 2018-05-15T04:46:37-0700 uid 0
> xlated 200B not jited memlock 4096B map_ids 4
> 7: kprobe name probe___x64_sys tag f2fdee479a503abf gpl
> loaded_at 2018-05-15T04:48:32-0700 uid 0
> xlated 200B not jited memlock 4096B map_ids 7
> 8: tracepoint name tracepoint__sys tag 5390badef2395fcf gpl
> loaded_at 2018-05-15T04:48:48-0700 uid 0
> xlated 200B not jited memlock 4096B map_ids 8
> 9: kprobe name probe_main_1 tag 0a87bdc2e2953b6d gpl
> loaded_at 2018-05-15T04:49:52-0700 uid 0
> xlated 200B not jited memlock 4096B map_ids 9
>
> $ ps ax | grep "python ./trace.py"
> 21711 pts/0 T 0:03 python ./trace.py __x64_sys_write
> 21765 pts/0 S+ 0:00 python ./trace.py r::__x64_sys_nanosleep
> 21767 pts/2 S+ 0:00 python ./trace.py t:syscalls:sys_enter_nanosleep
> 21800 pts/3 S+ 0:00 python ./trace.py p:/home/yhs/a.out:main
> 22374 pts/1 S+ 0:00 grep --color=auto python ./trace.py
>
> Signed-off-by: Yonghong Song <yhs@fb.com>
> ---
> tools/bpf/bpftool/main.c | 3 +-
> tools/bpf/bpftool/main.h | 1 +
> tools/bpf/bpftool/perf.c | 188 +++++++++++++++++++++++++++++++++++++++++++++++

Would you be able to also extend the Documentation/ and bash
completions?

> 3 files changed, 191 insertions(+), 1 deletion(-)
> create mode 100644 tools/bpf/bpftool/perf.c
>
> diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
> index 1ec852d..eea7f14 100644
> --- a/tools/bpf/bpftool/main.c
> +++ b/tools/bpf/bpftool/main.c
> @@ -87,7 +87,7 @@ static int do_help(int argc, char **argv)
> " %s batch file FILE\n"
> " %s version\n"
> "\n"
> - " OBJECT := { prog | map | cgroup }\n"
> + " OBJECT := { prog | map | cgroup | perf }\n"
> " " HELP_SPEC_OPTIONS "\n"
> "",
> bin_name, bin_name, bin_name);
> @@ -216,6 +216,7 @@ static const struct cmd cmds[] = {
> { "prog", do_prog },
> { "map", do_map },
> { "cgroup", do_cgroup },
> + { "perf", do_perf },
> { "version", do_version },
> { 0 }
> };
> diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
> index 6173cd9..63fdb31 100644
> --- a/tools/bpf/bpftool/main.h
> +++ b/tools/bpf/bpftool/main.h
> @@ -119,6 +119,7 @@ int do_prog(int argc, char **arg);
> int do_map(int argc, char **arg);
> int do_event_pipe(int argc, char **argv);
> int do_cgroup(int argc, char **arg);
> +int do_perf(int argc, char **arg);
>
> int prog_parse_fd(int *argc, char ***argv);
> int map_parse_fd_and_info(int *argc, char ***argv, void *info, __u32 *info_len);
> diff --git a/tools/bpf/bpftool/perf.c b/tools/bpf/bpftool/perf.c
> new file mode 100644
> index 0000000..6d676e4
> --- /dev/null
> +++ b/tools/bpf/bpftool/perf.c
> @@ -0,0 +1,188 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +// Copyright (C) 2018 Facebook
> +// Author: Yonghong Song <yhs@fb.com>
> +
> +#define _GNU_SOURCE
> +#include <fcntl.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <sys/stat.h>
> +#include <sys/types.h>
> +#include <unistd.h>
> +#include <ftw.h>
> +
> +#include <bpf.h>
> +
> +#include "main.h"
> +
> +static void print_perf_json(int pid, __u32 prog_id, __u32 prog_info,
> + char *buf, __u64 probe_offset, __u64 probe_addr)
> +{
> + jsonw_start_object(json_wtr);
> + jsonw_int_field(json_wtr, "pid", pid);
> + jsonw_uint_field(json_wtr, "prog_id", prog_id);
> + switch (prog_info) {
> + case BPF_PERF_INFO_TP_NAME:
> + jsonw_string_field(json_wtr, "prog_info", "tracepoint");
> + jsonw_string_field(json_wtr, "tracepoint", buf);
> + break;
> + case BPF_PERF_INFO_KPROBE:
> + jsonw_string_field(json_wtr, "prog_info", "kprobe");
> + if (buf[0] != '\0') {
> + jsonw_string_field(json_wtr, "func", buf);
> + jsonw_lluint_field(json_wtr, "offset", probe_offset);
> + } else {
> + jsonw_lluint_field(json_wtr, "addr", probe_addr);
> + }
> + break;
> + case BPF_PERF_INFO_KRETPROBE:
> + jsonw_string_field(json_wtr, "prog_info", "kretprobe");
> + if (buf[0] != '\0') {
> + jsonw_string_field(json_wtr, "func", buf);
> + jsonw_lluint_field(json_wtr, "offset", probe_offset);
> + } else {
> + jsonw_lluint_field(json_wtr, "addr", probe_addr);
> + }
> + break;
> + case BPF_PERF_INFO_UPROBE:
> + jsonw_string_field(json_wtr, "prog_info", "uprobe");
> + jsonw_string_field(json_wtr, "filename", buf);
> + jsonw_lluint_field(json_wtr, "offset", probe_offset);
> + break;
> + case BPF_PERF_INFO_URETPROBE:
> + jsonw_string_field(json_wtr, "prog_info", "uretprobe");
> + jsonw_string_field(json_wtr, "filename", buf);
> + jsonw_lluint_field(json_wtr, "offset", probe_offset);
> + break;
> + }
> + jsonw_end_object(json_wtr);
> +}
> +
> +static void print_perf_plain(int pid, __u32 prog_id, __u32 prog_info,
> + char *buf, __u64 probe_offset, __u64 probe_addr)
> +{
> + printf("%d: prog_id %u ", pid, prog_id);

nit: for consistency with prog and map listings consider using double
spaces after prog_id (i.e. between fields). Not a hard requirement,
though, perhaps I'm the only one who finds that more readable :)

> + switch (prog_info) {
> + case BPF_PERF_INFO_TP_NAME:
> + printf("tracepoint %s\n", buf);
> + break;
> + case BPF_PERF_INFO_KPROBE:
> + if (buf[0] != '\0')
> + printf("kprobe func %s offset %llu\n", buf,
> + probe_offset);
> + else
> + printf("kprobe addr %llu\n", probe_addr);
> + break;
> + case BPF_PERF_INFO_KRETPROBE:
> + if (buf[0] != '\0')
> + printf("kretprobe func %s offset %llu\n", buf,
> + probe_offset);
> + else
> + printf("kretprobe addr %llu\n", probe_addr);
> + break;
> + case BPF_PERF_INFO_UPROBE:
> + printf("uprobe filename %s offset %llu\n", buf, probe_offset);
> + break;
> + case BPF_PERF_INFO_URETPROBE:
> + printf("uretprobe filename %s offset %llu\n", buf,
> + probe_offset);
> + break;
> + }
> +}
> +
> +static int show_proc(const char *fpath, const struct stat *sb,
> + int tflag, struct FTW *ftwbuf)
> +{
> + __u64 probe_offset, probe_addr;
> + __u32 prog_id, prog_info;
> + int err, pid = 0, fd = 0;
> + const char *pch;
> + char buf[4096];
> +
> + /* prefix always /proc */
> + pch = fpath + 5;
> + if (*pch == '\0')
> + return 0;
> +
> + /* pid should be all numbers */
> + pch++;
> + while (*pch >= '0' && *pch <= '9') {

nit: isdigit()? strtoul() with its endptr also an option. That said
the code is actually quite readable as is, so I'm not sure if it's
worth complicating it.

> + pid = pid * 10 + *pch - '0';
> + pch++;
> + }
> + if (*pch == '\0')
> + return 0;
> + if (*pch != '/')
> + return FTW_SKIP_SUBTREE;
> +
> + /* check /proc/<pid>/fd directory */
> + pch++;
> + if (*pch == '\0' || *pch != 'f')
> + return FTW_SKIP_SUBTREE;

but == '\0' implies != 'f'

> + pch++;
> + if (*pch == '\0' || *pch != 'd')
> + return FTW_SKIP_SUBTREE;

nit: possibly just:
if (strncmp(pch, "fd", 2))
return FTW_SKIP_SUBTREE;
pch += 2;

> + pch++;
> + if (*pch == '\0')
> + return 0;
> + if (*pch != '/')
> + return FTW_SKIP_SUBTREE;
> +
> + /* check /proc/<pid>/fd/<fd_num> */
> + pch++;
> + while (*pch >= '0' && *pch <= '9') {
> + fd = fd * 10 + *pch - '0';
> + pch++;
> + }
> + if (*pch != '\0')
> + return FTW_SKIP_SUBTREE;
> +
> + /* query (pid, fd) for potential perf events */
> + err = bpf_trace_event_query(pid, fd, buf, sizeof(buf),
> + &prog_id, &prog_info, &probe_offset, &probe_addr);

nit: continuation line not aligned with opening bracket

> + if (err < 0)
> + return 0;
> +
> + if (json_output)
> + print_perf_json(pid, prog_id, prog_info, buf, probe_offset,
> + probe_addr);
> + else
> + print_perf_plain(pid, prog_id, prog_info, buf, probe_offset,
> + probe_addr);
> +
> + return 0;
> +}
> +
> +static int do_show(int argc, char **argv)
> +{
> + int nopenfd = 16;
> + int flags = FTW_ACTIONRETVAL | FTW_PHYS;

nit: reverse christmas tree networking style if you don't mind

> + if (nftw("/proc", show_proc, nopenfd, flags) == -1) {
> + perror("nftw");

nit: p_err("%s", strerror(errno)); would also show up in JSON output

> + return -1;
> + }
> +
> + return 0;
> +}
> +
> +static int do_help(int argc, char **argv)
> +{
> + fprintf(stderr,
> + "Usage: %s %s { show | help }\n"
> + "",
> + bin_name, argv[-2]);
> +
> + return 0;
> +}
> +
> +static const struct cmd cmds[] = {
> + { "show", do_show },

Other commands alias show and list, so could you add:

{ "list", do_show },

and list to help output?

> + { "help", do_help },
> + { 0 }
> +};
> +
> +int do_perf(int argc, char **argv)
> +{
> + return cmd_select(cmds, argc, argv, do_help);
> +}

Thanks a lot for adding bpftool support, and with JSON output included!